Deal with the edge case of dragging from shelf while typing

The edge case of dragging the shelf while typing in the search
box is not taken into consideration. As result, when the
expected app list view state is FULLSCREEN_SEARCH, its actual
state is FULLSCREEN_ALL_APPS. This CL fixes the problem.

In addition, refactor the code: move the code block, which is for
calculating the app list view state after shelf drag, from
ShelfLayoutManager to AppListView.


Test: None
Bug: 919205
Change-Id: I39aa095bbd1a9417d07b50cc6caed1084fde5f4d
Reviewed-on: https://chromium-review.googlesource.com/c/1462419
Commit-Queue: Andrew Xu <andrewxu@chromium.org>
Reviewed-by: Xiyuan Xia <xiyuan@chromium.org>
Cr-Commit-Position: refs/heads/master@{#631795}
9 files changed